JPS6213495B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a negative pressure control device, and more particularly to a negative pressure control device having desired control characteristics depending on engine characteristics.

[Conventional technology and problems]

Conventional internal combustion engines are often provided with a control valve device that opens and closes a passage in response to intake pipe negative pressure. For example, a passage for supplying secondary air to the upstream side of the catalytic converter in the exhaust pipe, a passage for exhaust circulation connecting the exhaust manifold and the intake manifold, or a passage for supplying bleed air to the carburetor.
BACKGROUND ART Control valve devices that open and close in response to control pipe negative pressure are conventionally known. The secondary air supply passage is opened and closed to maintain the temperature of the catalyst at a constant value in order to promote the purification action of the catalyst when the engine is started, and after that, to ensure the purification action of the catalyst, the exhaust gas is must be opened and closed to maintain the stoichiometric air-fuel ratio. The exhaust circulation passage must be opened and closed so that the exhaust gas flow rate changes according to the engine operating state, in order to prevent deterioration in engine operability due to knocking and reduce NOx in the exhaust. Furthermore, in order to control the air-fuel ratio of the air-fuel mixture with high precision, the bleed air supply passage must be opened and closed so as to adjust the bleed air flow rate with high precision according to the engine operating state. The negative pressure control device for opening and closing the control valve devices in each of the passages described above operates to supply intake pipe negative pressure or atmospheric pressure to the control valve device with high accuracy depending on the engine operating state. is required.

JP-A-51-149416 and JP-A-51-
Publication No. 101623 discloses that the inside of the housing is divided by two diaphragms to form first and second diaphragm chambers, these diaphragm chambers are communicated upstream and downstream of the throttle valve, respectively, and the diaphragm is injected with secondary air. A device is disclosed in which a valve body for opening and closing a supply passage is connected.
However, this conventional device has limited elements for adjusting the valve opening characteristics of the valve body, and the valve opening characteristics cannot be adjusted freely, making it difficult to open and close the passage with high precision according to the engine operating state. Have difficulty.

[Means for solving problems]

The negative pressure control device according to the present invention partitions the housing by first and second diaphragms to form first and second diaphragm chambers and a relief chamber,
The first and second diaphragm chambers are connected to a port of the intake passage which opens upstream of the throttle valve and the intake passage downstream of the throttle valve, respectively, and the relief chamber is connected to the atmosphere. A connection spring that elastically connects the diaphragms is provided, a first spring that biases the first diaphragm toward the second diaphragm chamber is provided in the first diaphragm chamber, and a second diaphragm is provided in the relief chamber. It is characterized in that a second spring that presses toward the chamber is provided, and an operating member that can operate a switch is connected to the second diaphragm. The operating member is displaced in response to the pressure introduced into the first and second diaphragm chambers to switch the switch, and the switching characteristic is to change the characteristics of the connecting spring, the first and second springs, and the first and second diaphragm. Adjusted by

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the negative pressure control device of the present invention is used to control the operation of a secondary air supply device.
drives an air pump 5 by means of a belt 3, communicates with a carburetor 9 via an intake passage (intake manifold) 7, and connects to a catalytic converter 13 such as a three-way catalyst via an exhaust passage (exhaust manifold) 11. is connected to. The air pump 5 and the exhaust passage 11 are communicated through the secondary air supply pipes 15 and 17 and the secondary air supply control valve device 19, and the secondary air is supplied to the exhaust passage 11 and the exhaust gas is discharged by the action of the catalytic converter 13. Reduce harmful components such as CO, HC and NOx. The secondary air supply control valve device 19 includes a working chamber 25 defined by a diaphragm 21 . A spring 23 for pressing the diaphragm 21 is installed in the working chamber 25, and is further communicated with the intake pipe 7 via the working negative pressure supply pipe 27. A conical valve body 31 is fixed to the diaphragm 21 via a valve rod 29,
The valve body 31 moves against the valve seat 3 according to the movement of the diaphragm 21.
Make it work together with 3. With this, the valve body 31
The amount of secondary air supplied from the secondary air supply pipe 15 to the other secondary air supply pipes 17 is controlled by this function. Port 35 opens directly to the atmosphere or communicates with an air filter (not shown) to recirculate excess secondary air. The carburetor 9 shown in FIG. 1 has a throttle valve 41 that can swing in conjunction with an accelerator pedal (not shown). A fuel jet 49 is opened in a bench lily section 45 provided upstream of the throttle valve 41, and the fuel in the float chamber 53 is supplied to the bench lily section 45, where it is mixed with air taken in from an air filter (not shown) to form a combustible air-fuel mixture. Prepare.

The above structure is the same as that of a conventional internal combustion engine with a secondary air supply device.

Negative pressure control device 159 includes first diaphragm 163
The second diaphragm 165 divides the chamber into a first diaphragm chamber 167, a second diaphragm chamber 169, and a relief chamber 171. The first diaphragm 163 is inserted into the first diaphragm chamber 167.
The first spring 17 presses against the diaphragm chamber 169 side.
Attach 3. The first diaphragm chamber 169
Diaphragm 163 and second diaphragm 16
A connecting spring 175 is provided to elastically connect the two.
A second spring 179 is provided in the relief chamber 171 to fix the operating member 177 to the surface of the second diaphragm 165 on the relief chamber 171 side and to press the second diaphragm 165 toward the second diaphragm chamber 169 side. Also, the operation member 177 is opposite to the operation member 177.
An electric switch 161 operated by the switch 7 is provided on the wall of the relief chamber 171. The first diaphragm chamber 167 is communicated with the throttle port 181 via the negative pressure pipe 79. The throttle port 181 is provided between the vent lily portion 45 of the carburetor 9 and the throttle valve 41 at a position that is approximately at the same position as the valve edge of the throttle valve 41 when the throttle valve 41 is fully opened. Therefore, the first diaphragm chamber 167 is filled with the throttle negative pressure P _S from the throttle port 181. The second diaphragm chamber 169 is connected to the negative pressure pipe 85
It communicates with a port 87 that opens into the intake passage 7 downstream of the throttle valve 41 through the throttle valve 41 . Therefore, the second diaphragm chamber 169 is filled with the intake pipe negative pressure P _I from the port 87. On the other hand, the relief chamber 171 communicates with the atmosphere. First biasing spring 173, connection spring 1
75 and the second pressing spring 179 are respectively set as W ₁ , W ₂ and W ₃ , and the first diaphragm 1
When the areas S ₁ and S ₂ of the second diaphragm 163 and the second diaphragm 165 are equal, the condition for the operating member 177 to turn on the electric switch 161 is expressed by equation (1). Note that K ₁ , K ₂ and K ₃ are springs 173, 17
Spring constant of 5,179, L is spring 173,175
is the sum of the amount of distortion.

₀ < _{( K2L} + _PIS1 - _PSS1 ) _K1 / _K1 + _K2
+P _S S ₁ -W ₃ (1) The electric switch 161 is connected to a three-way solenoid valve device 183 via a computer 182,
When the electric switch 161 is off, the intake negative pressure P _I in the intake passage 7 is supplied to the secondary air supply control valve device 19 through the operating negative pressure supply pipe 27, and secondary air is supplied to the exhaust passage 11. On the other hand, electric switch 161
When turned on, the supply of intake pipe negative pressure P _I from the intake passage 7 is stopped, and at the same time, the three-way switching solenoid valve device 18
Atmospheric pressure is supplied from the relief port No. 3 to the secondary air supply control valve device 19, thereby cutting off the supply of secondary air.

Next, referring to FIG. 2, it will be explained that the characteristics of the negative pressure control device according to the embodiment of the present invention are preferable for shutoff control of the secondary air supply valve device. In FIGS. 2a to 2c, the horizontal axis represents the engine speed, and the vertical axis represents the intake pipe negative pressure. FIG. 2a shows the isotemperature curve of the catalytic converter 13 (FIG. 1). As can be seen from this figure, the isotemperature curve of the catalytic converter is a steep upward-sloping curve. Therefore, the secondary air control valve device 1
9 (FIG. 1) along a particular catalytic converter isotemperature curve shown by dashed line _C in FIG. This can prevent overheating. However, the conventional negative pressure control valve device operated by the ventilator pressure P _V has a shutoff characteristic as shown by the chain line A in Fig. 2b, which may cause the catalytic converter to overheat, or conversely cause the catalytic converter to not operate properly. There was a problem that it could not be used.

The device according to the embodiment of the present invention shuts off according to the above-mentioned equation (1). On the other hand, the throttle negative pressure P _S has a characteristic as shown in FIG. 2c. By selecting the characteristics of the first and second diaphragms 163, 165 and the springs 173, 175 and 179 so that the throttle negative pressure P _S and the intake pipe negative pressure P _I satisfy the above-mentioned equation (1). A negative pressure control device having a shutoff characteristic as shown by the solid line B in FIG. 2b can be obtained.

Note that the ports communicating with the first diaphragm chamber 167 and the second diaphragm chamber 169 may be replaced.

Further, the switch 161 is not limited to an electric switch.

In the above embodiment, a negative pressure control device is used to drive a control valve device that opens and closes a secondary air supply passage. Of course, it can be applied to drive devices.

〔Effect of the invention〕

The negative pressure control device of the present invention has a simple structure, and the desired operating characteristics can be achieved very easily. Furthermore, the operating characteristics can be freely adjusted and set with high precision by selecting the characteristics of the first and second diaphragms, the first and second springs, and the connection spring. Therefore, opening and closing of passages such as the secondary air supply passage, the exhaust circulation passage, and the bleed air supply passage can be controlled with high precision according to the engine operating state.

[Brief explanation of the drawing]

Fig. 1 is a sectional front view of an embodiment of the present invention, Fig. 2a is a temperature characteristic diagram of the catalytic converter, Fig. 2b is a cutoff characteristic diagram of the secondary air supply control valve device, and Fig. 2c is a throttle negative FIG. 87... Port, 159... Negative pressure control device, 1
61... Electric switch, 163... First diaphragm, 165... Second diaphragm, 167...
First diaphragm chamber, 169... Second diaphragm chamber, 171... Relief chamber, 173... First spring, 175... Connection spring, 177... Operating member,
179...second spring, 181...throttle port.

Claims (1)

[Claims] 1 A negative pressure control device that drives and controls a control valve device that opens and closes a passage of an internal combustion engine according to intake pipe negative pressure, which is provided with a switch for controlling introduction of intake pipe negative pressure to the control valve device. , the housing is partitioned by first and second diaphragms to form first and second diaphragm chambers and a relief chamber;
The second diaphragm chamber is communicated with a port opened upstream of the throttle valve in the intake passage and the intake passage downstream of the throttle valve, and the relief chamber is communicated with the atmosphere. A first spring is provided in the first diaphragm chamber to bias the first diaphragm toward the second diaphragm chamber, and the second diaphragm is biased toward the second diaphragm chamber in the relief chamber. 1. A negative pressure control device comprising: a second spring that presses the switch; and an operating member that operates the switch connected to the second diaphragm.